Active matrix display devices having improved opening and contrast ratios and methods of forming same

ABSTRACT

Active matrix display devices having improved opening and contrast ratios utilize light blocking lines to improve display contrast ratios yet position the light blocking lines on the same level of metallization as the gate lines to thereby limit parasitic capacitive coupling between the data lines and the pixel electrodes. The light blocking lines are also positioned on only one side of the data lines so that improvements in the display&#39;s opening ratio can also be achieved. The light blocking lines are preferably patterned so that no overlap occurs between a display&#39;s data lines and the light blocking lines. The elimination of overlap reduces the step height in the display&#39;s pixel electrodes and thereby reduces the extent of disclination of the liquid crystal molecules in the liquid crystal material extending opposite the pixel electrodes. The light blocking lines are also preferably patterned beneath the display&#39;s data lines so that parasitic capacitive coupling between the data lines and the pixel electrodes is reduced. The light blocking lines are also preferably formed with beveled edges so that the step height in the display&#39;s pixel electrodes can be reduced even further.

FIELD OF THE INVENTION

[0001] The present invention relates to display devices and methods offorming display devices, and more particularly to liquid crystal displaydevices and methods of forming liquid crystal display devices.

BACKGROUND OF THE INVENTION

[0002] In order to minimize the space required by display devices,research into the development of various flat panel display devices suchas LCD display devices, plasma display panels (PDP) andelectro-luminescence displays (EL), has been undertaken to displacelarger cathode-ray tube displays (CRT) as the most commonly used displaydevices. Particularly, in the case of LCD display devices, liquidcrystal technology has been explored because the optical characteristicsof liquid crystal material can be controlled in response to changes inelectric fields applied thereto. As will be understood by those skilledin the art, a thin film transistor liquid crystal display (TFT LCD)typically uses a thin film transistor as a switching device and theelectrical-optical effect of liquid crystal molecules to display datavisually.

[0003] At present, the dominant methods for fabricating liquid crystaldisplay devices and panels are typically methods based on amorphoussilicon (a-Si) thin film transistor technologies. Using thesetechnologies, high quality image displays of substantial size can befabricated using low temperature processes. As will be understood bythose skilled in the art, conventional LCD devices typically include atransparent (e.g., glass) substrate with an array of thin filmtransistors thereon, pixel electrodes, orthogonal gate and data lines, acolor filter substrate and liquid crystal material between thetransparent substrate and color filter substrate. The use of a-Si TFTtechnology typically also requires the use of separate peripheralintegrated circuitry to drive the gates and sources (i.e., data inputs)of the TFTs in the array. In particular, gate driving signals from agate driving integrated circuit are typically transmitted to the gateelectrodes of TFTs in respective rows and data driving signals from adata driving integrated circuit are typically transmitted to the sourceelectrodes of TFTs in respective columns. A display is typicallycomposed of a TFT substrate in which a plurality of liquid crystalpixels are formed. Each pixel typically has at least one TFT and a pixelelectrode coupled to the drain of the respective TFT. Accordingly, theapplication of a gate driving signal to the gate of a TFT willelectrically connect the pixel electrode of a respective TFT to the dataline connected thereto.

[0004] Referring now to FIGS. 1-3, an active matrix substrate of aconventional TFT LCD with a light blocking film will be described. Thisand other TFT LCDs are more fully described in U.S. Pat. No. 5,426,523to Shimada et al. In particular, FIG. 1 is a plan view showing aconventional active matrix display device. FIG. 2 is a cross-sectionalview of the active matrix display device of FIG. 1, taken along lineA-A′ and FIG. 3 is a cross-sectional view of the active matrix displaydevice of FIG. 1, taken along line B-B′. As illustrated by FIG. 1, agate line 130 is formed in a horizontal direction, and a data line 150crosses the gate line 130. A light blocking film 8, with a width largerthan that of the data line 150, is formed on each data line 150. Each ofthe side excess portions over the data line 150 in the transversedirection is set to a length “d”. In each region defined by the gate anddata lines, a pixel electrode 7 is formed so that both sides of thepixel electrode 7 overlap the neighboring blocking films and data linesby a constant length. In each pixel region, a TFT is formed.Specifically, the region of a silicon film 110 under the branch of thegate line 130 forms a gate of the TFT, the region of the silicon film110 connected to the data line 150 by way of a contact hole 4 a forms asource of the TFT, and the region of the silicon film 110 connected tothe pixel electrode 7 by way of a contact hole 4 b forms a drain of theTFT. If a turn-on voltage is applied to the gate line 130, a conductionpath between source and drain becomes active due to the ON state of theTFT, and, therefore a video signal from the data line 150 can betransmitted to the pixel electrode 7 via the silicon film 110.

[0005] Referring now to FIG. 2, a silicon film 110 is formed on atransparent substrate 100, and serves as a source electrode, a drainelectrode and a semiconductor active layer of the TFT. A gate insulatingfilm 120 is formed on the silicon film 110 and the transparent substrate100 so as to cover the entire surface. On a certain region of the gateinsulating film 120, a gate electrode 130 is formed. Moreover, aninsulating film 140 is formed on the entire surface of the gateelectrode 130 and the gate insulating film 120. A contact hole 4 a isformed through the gate insulating film 120 and the insulating film 140.On the insulating film 140, the data line 150 is formed and connected tothe silicon film 110 via the contact hole 4 a.

[0006] On the entire surface of the insulating film 140 and the dataline 150, a passivation film 160 is formed, and a contact hole 4 b isformed through the gate insulating film 120, the insulating film 140 andthe passivation film 160. A pixel electrode 7, made of anindium-tin-oxide (ITO) film, is formed on the passivation film 160 andconnected to the silicon film 110 via the contact hole 4 b. A videosignal received from the data line 150 passes through the silicon film110 via the contact hole 4 a, and, then, is transmitted to the ITO pixelelectrode 7 via the contact hole 4 b. The TFT with such a structurewhere the gate electrode 130 is located on the semiconductor layer iscalled a top gate type TFT.

[0007] A cross-sectional structure of the prior active matrix substratecoupled with a liquid crystal layer and a counter substrate will now bedescribed with reference to FIG. 3. Here, a gate insulating film 120 isformed on a transparent substrate 100, and a data line 150 is formedthereon. A passivation film 160 is formed on the entire film of the gateinsulating film 120 and the data line 150, and a light blocking film 8is formed on the passivation film so as to cover a certain region of thepassivation film over the data line 150. An insulating film 180 isformed on the entire surface of the light blocking film 8 and thepassivation film 160, and an ITO pixel electrode 7 is formed thereon. Inthe above mentioned structure of the prior active matrix substrate, thedata line 150 has a thickness of 500 nm, and is usually formed ofaluminum (Al). The passivation film 160 is formed of silicon oxide(SiOx) having a thickness of 400 nm. Furthermore, the light blockingfilm 8 having a thickness of 100 nm is formed of the same material asthe data line 150, and each of the lengths “d” of the side excessportions of the light blocking film 8 over the data line 150 in thetransverse direction, is set to be 5 μm.

[0008] A counter substrate 200, including a transparent counterelectrode 210 formed on the surface thereof, is attached to the activematrix substrate. Into a space between the two substrates, liquidcrystal is injected to form the liquid crystal layer 190, and thethickness of the liquid crystal layer 190 is set to be about 5 μm. Here,even though abnormal light leakage occurs due to the orientationdisorder of the liquid crystal molecules in the edge regions of the dataline 150 (caused by a step of the data line 150), the light leakage canbe blocked considerably since the light blocking film 8 is broader thanthe data line 150 and is formed to cover the data line 150. In thesecircumstances, the orientation disorder of the liquid crystal moleculesby a step of the light blocking film 8 can be negligible, since thethickness of the light blocking film 8 is very small than that of thedata line 150.

[0009] However, some light leakage still remains due to the considerablestep of the data line 150. Especially, in a normally white mode display,the vicinity of the step of the data line 150 is not absolutely blackeven when a voltage is applied to the liquid crystal for a blackdisplay. Thus, the contrast of the display apparatus is degraded. Inaddition, the opening ratio of the liquid crystal display apparatus ismade smaller since the light blocking film 8 is formed to exceed 5 μm atits side portions over the data line 150 and thus covers the pixelelectrode 7 with its excess regions.

[0010] In the illustrated display device, the light blocking film 8 islocated between the pixel electrode 7 and the data line 150 whileoverlapping one another. Accordingly, the capacitive coupling betweenthe pixel electrode 7 and the data line 150 increases because the lightblocking film 8 serves as an intermediate conductive layer. Moreover,the fabrication of this structure where the light blocking film 8 isformed on the data line 150 increases manufacturing cost since itrequires additional processes such as metal deposition and etching.

[0011] Thus, notwithstanding the above described prior art active matrixliquid crystal display devices, there continues to be a need forimproved liquid crystal display devices which have high contrast andopening ratios and are less susceptible to light leakage caused bydisordered or misaligned liquid crystal molecules.

SUMMARY OF THE INVENTION

[0012] It is therefore an object of the present invention to provideimproved liquid crystal display (LCD) devices and methods of formingsame.

[0013] It is another object of the present invention to provide liquidcrystal display devices having improved opening ratios and methods offorming same.

[0014] It is a further object of the present invention to provide liquidcrystal display devices having improved contrast ratios and methods offorming same.

[0015] It is still a further object of the present invention to provideliquid crystal display devices having light blocking lines which do notcontribute to parasitic capacitive coupling between data lines and pixelelectrodes, and methods of forming same.

[0016] These and other objects, advantages and features of the presentinvention are provided by liquid crystal display devices which havingpixel electrodes, data lines and gate lines and utilize light blockinglines to improve display contrast ratios yet position the light blockinglines on the same level of metallization as the gate lines to therebylimit parasitic capacitive coupling between the data lines and the pixelelectrodes. In addition, the light blocking lines are positioned on onlyone side of the data lines so that improvements in the display's openingratio can also be achieved.

[0017] In particular, according to the present invention, liquid crystaldisplay devices comprise an array of liquid crystal display cells (e.g.,TFT display cells) and a plurality of light blocking lines to improvethe contrast ratios of the display devices. The light blocking lines arepreferably patterned so that no overlap occurs between a display's datalines and the light blocking lines. The elimination of overlap reducesthe step height in the display's pixel electrodes and thereby reducesthe extent of disclination of the liquid crystal molecules in the liquidcrystal material extending opposite the pixel electrodes. The lightblocking lines are also preferably patterned beneath the display's datalines so that parasitic capacitive coupling between the data lines andthe pixel electrodes is reduced. Moreover, although the light blockinglines are formed parallel to the data lines, they are preferably formedon only one side of the data lines so that improved opening ratios canbe achieved. The light blocking lines are also preferably formed withbeveled edges so that the step height in the display's pixel electrodescan be reduced even further. Thus, the light blocking lines are formedto compensate for light leakage (which may occur because of the presenceof parasitic electric fields between a display's data lines and pixelelectrodes during operation) yet still maintain the degree ofdisclination of the liquid crystal molecules at a low level by allowingthe pixel electrodes to be formed with reduced step height.

[0018] According to one embodiment of the present invention, a liquidcrystal display device comprises a transparent substrate having a facethereon, and first and second display cells on the substrate. The firstdisplay cell contains a first pixel electrode and has a control input(e.g., gate electrode of a TFT) electrically coupled to a first gateline. The second display cell contains a second pixel electrode and acontrol input electrically coupled to a second gate line. A first lightblocking line is also provided on the substrate. The first lightblocking line is preferably electrically coupled to the first gate lineby patterning the first gate line and the first light blocking lineusing the same level of metallization. A first data line is alsoprovided on the substrate. According to a preferred aspect of thepresent invention, the first data line overlaps the first and secondpixel electrodes by not the first light blocking line. The first dataline is also preferably formed at a higher level of metallizationrelative to the first light blocking line so that, among other things,parasitic capacitive coupling between the first data line and the firstand second pixel electrodes can be maintained at a relatively low level.

[0019] According to another embodiment of the present invention, aliquid crystal display device comprises an array of liquid crystaldisplay cells on a transparent substrate, arranged as a plurality ofrows and columns of display cells. A plurality of data lines are alsoprovided on the substrate so that each data line is disposed betweenadjacent columns of display cells. A plurality of ladder-shapedelectrodes are also provided on the substrate and each of theladder-shaped electrodes is disposed opposite a row of display cells sothat the pixel electrodes in each row of display cells overlap arespective ladder-shaped electrode. The ladder-shaped electrodes arealso preferably formed with beveled edges to improve the planaruniformity of the subsequently formed pixel electrodes and reduce theextent of disclination between the liquid crystal molecules in theliquid crystal material extending opposite the pixel electrodes.

[0020] The present invention also includes methods of forming liquidcrystal display devices having improved opening and contrast ratios. Inparticular, according to yet another embodiment of the presentinvention, a method of forming a liquid crystal display device (e.g.,active matrix display) includes the steps of forming a first conductivelayer (e.g., aluminum) on a face of a transparent substrate and thenpatterning the first conductive layer to define a ladder-shapedelectrode having first and second side electrodes and a plurality ofrungs electrically interconnecting the first and second side electrodes.A first electrically insulating layer (e.g., SiO₂) is then formed on theladder-shaped electrode. Next, a layer of amorphous silicon (a-Si) isformed on the first electrically insulating layer. The layer ofamorphous silicon is then patterned to define an amorphous siliconactive region extending opposite a portion of the first side electrode.A second conductive layer is then formed on the first electricallyinsulating layer and amorphous silicon active region. The secondconductive layer is then patterned into a data line and a drainelectrode so that the data line and drain electrode contact first andsecond portions of the amorphous silicon active region, respectively. Asecond electrically insulating layer (e.g., Si₃N₄) is then formed on thepatterned second conductive layer and then patterned to expose a portionof the drain electrode. A layer of indium-tin-oxide (ITO) is thendeposited and patterned to define a pixel electrode which iselectrically connected to the exposed portion of the drain electrode.

[0021] Thus, the present invention provides for liquid crystal displaydevices having improved contrast ratios by incorporating light blockinglines therein. The light blocking lines are also patterned so that anystep height in the display's pixel electrodes is maintained at a lowlevel so that the degree of disclination in the liquid crystal materialis reduced. This is achieved by patterning the light blocking lines sothat they do not overlap the display's data lines. In addition, thelight blocking lines are preferably positioned on only one side of thedata lines so that improved opening ratios can be achieved. Theparasitic loading capacitance between the data lines and pixelelectrodes can also be improved by patterning the light blocking linesbelow the data lines, using the same level of metallization as used toform the gate lines.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 is a layout schematic view of a liquid crystal displaydevice according to the prior art.

[0023]FIG. 2 is a cross-sectional view of the liquid crystal displaydevice of FIG. 1, taken along line A-A′.

[0024]FIG. 3 is a cross-sectional view of the liquid crystal displaydevice of FIG. 1, taken along line B-B′.

[0025]FIG. 4 is a layout schematic view of an active matrix liquidcrystal display device according to the present invention.

[0026]FIG. 5 is a cross-sectional view of a first embodiment of thedevice of FIG. 4, taken along line C-C′.

[0027]FIG. 6 is a cross-sectional view of a second embodiment of thedevice of FIG. 4, taken along line C-C′.

[0028]FIG. 7 is a cross-sectional view of a third embodiment of thedevice of FIG. 4, taken along line C-C′.

[0029]FIG. 8 is a cross-sectional view of an embodiment of the device ofFIG. 4, taken along line D-D′.

[0030]FIG. 9 is a cross-sectional view of another embodiment of thedevice of FIG. 4, taken along line D-D′.

[0031]FIG. 10 is an electrical schematic of an active matrix liquidcrystal display device according to an embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0032] The present invention will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. This invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. Like numbers refer to like elements throughout.

[0033] Referring to FIGS. 4 and 10, layout and electrical schematicdiagrams of an active matrix liquid crystal display device according tothe present invention will now be described. In particular, an activematrix liquid crystal display device is provided which comprises atwo-dimensional array of thin-film transistor (TFT) liquid crystaldisplay cells arranged as a plurality of columns of display cells and aplurality of rows of display cells.

[0034] As illustrated, each column of display cells is defined betweenadjacent data lines 150 (e.g., D_(j-2), D_(j-1), . . . , D_(j+1)) andeach row of display cells is defined between adjacent gate lines 130 a(e.g., G_(i-2), G_(i-1), . . . , G_(i+2)). Each display cell maycomprise an amorphous silicon (a-Si) thin-film field effect transistor(TFT) having a source region electrically coupled to a correspondingdata line 150 via an orthogonal data line extension, a gate electricallycoupled to a corresponding gate line 130 a and a drain regionelectrically coupled to a respective pixel electrode 7 preferably formedof a transparent material such as indium-tin-oxide (ITO). Each displaycell also preferably comprises a storage capacitor (C_(s)). As will beunderstood by those skilled in the art, the value of the storagecapacitor is a function of, among other things, the area of overlapbetween a pixel electrode 7 and an electrode coupled to an adjacentlower order gate line. As best illustrated by FIG. 4, the value of thestorage capacitor is a function of the area of overlap between eachpixel electrode 7 and an underlying ladder-shaped electrode which, asdescribed more fully hereinbelow, is comprised of a gate line 130 a, alight blocking line 9 and a storage electrode line 130 b. A liquidcrystal capacitor C_(LC) is also defined by each cell as the capacitancebetween a pixel electrode on a lower TFT substrate and a counterelectrode 210 on an upper counter substrate 200. As illustrated, thecounter electrode 210 may be biased to a common potential (V_(com)).

[0035] Referring again to FIG. 4, the data lines 150 are preferablypatterned as a plurality of parallel lines of metallization and each rowof display cells is defined opposite a respective ladder-shapedelectrode which is comprised of a plurality of light blocking lines 9 atthe rungs of the ladder-shaped electrode, a gate line 130 a and astorage electrode line 130 b which extends parallel to the gate line 130a. According to a preferred aspect of the present invention, each lightblocking line 9 is defined in parallel with a corresponding data line150, however, these lines are spaced laterally from each other so thereis no overlap between them. This reduces the extent of any parasiticcapacitive coupling between the data lines 150 and the light blockinglines 9. Moreover, because each light blocking line 9 is located on onlyone side of a respective data line 150 and pixel electrode 7, incontrast to the prior art active matrix substrates where both sides of apixel electrode extend opposite a light blocking line, the opening ratioof the liquid crystal display device is increased. As described morefully hereinbelow, the location of each light blocking line 9 relativeto a respective pixel electrode 7 is a function of the angle oforientation of the liquid crystal molecules in the liquid crystalmaterial which separates the lower TFT substrate 100 from the uppercounter substrate 200. As illustrated, the light blocking lines 9 arelocated on the left side of the pixel electrodes to correspond to theangle of orientation of the liquid crystal molecules 190′ illustrated byFIGS. 5-7.

[0036] Referring now to FIGS. 5-8, cross-sectional views of variousembodiments of the device of FIG. 4 are illustrated. In particular, thedisplay device of FIG. 4 may be formed by forming a first conductivelayer (e.g., aluminum, titanium, tungsten and alloys thereof) on a faceof a transparent substrate 100 and then patterning the first conductivelayer as a ladder-shaped electrode comprised of a plurality of lightblocking lines 9 (at the rungs of the ladder-shaped electrode), a gateline 130 a and storage electrode line 130 b. In FIG. 8, the illustratedcross-sections of the gate line 130 a and the storage electrode line 130b are part of adjacent ladder-shaped electrodes. The first conductivelayer may be formed to have a thickness of about 2,000 Å. After thefirst conductive layer has been patterned to define a plurality ofladder-shaped electrodes, the edges of the ladder-shaped electrodes arebeveled, using conventional techniques, to reduce the abruptness oftheir cross-sectional profile to subsequently formed layers. A firstelectrically insulating layer 120 (e.g., SiO₂) is then formed on thepatterned first conductive layer and face of the transparent substrate100, as illustrated.

[0037] Next, a layer of amorphous silicon (a-Si) is formed on the firstelectrically insulating layer 120 and then patterned to define aplurality of amorphous silicon active regions 110 of subsequently formedTFTs. Then, a blanket second electrically conductive layer, which mayhave thickness of less than about 2,000 Å, is formed on the firstelectrically insulating layer 120 and active regions 110. The secondelectrically conductive layer is then patterned using conventionaltechniques to define (i) a plurality of parallel data lines 150 whichhave orthogonal extensions in ohmic contact with source region portionsof the active regions 110, and (ii) a plurality of drain electrodes 170in ohmic contact with drain region portions of the active regions 110. Asecond electrically insulating region 160 is then formed on thepatterned second electrically conductive layer. This second electricallyinsulating layer 160 may comprise an inorganic passivation layer ofsilicon nitride (Si₃N₄) having a thickness of less than about 4,000 Å,for example. The second electrically insulating layer 160 is thenpatterned to define a plurality of openings therein which exposerespective drain electrodes 170 of the display cells. An opticallytransparent layer of indium-tin-oxide is then formed on the secondelectrically insulating layer 160 and patterned to define a plurality ofpixel electrodes 7. As illustrated, the opposing ends of adjacent pixelelectrodes preferably overlap opposing edges of each data line 150.

[0038] As best illustrated by FIG. 5, a upper counter substrate 200containing a counter electrode 210 is then mounted in spaced relationopposite the lower TFT substrate 100. As will be understood by thoseskilled in the art, liquid crystal material is then injected into thespace between the lower and upper substrates to define a liquid crystalmaterial layer 190 having a pre-tilt angle. As will be understood bythose skilled in the art, the tilt of the liquid crystal molecules 190′in the liquid crystal material layer 190 is influenced by the magnitudeof the vertical electric field which can be established between eachpixel electrode 7 and the counter electrode 210. However, near thevicinity of each data line 150, the tilt orientations of the liquidcrystal molecules 190′ in the liquid crystal material 190 are altered orscattered by stray and horizontal electric fields in the gap betweenadjacent pixel electrodes 7. As illustrated, the stray electric fieldsmay be sufficient to switch the pre-tilt orientation of the liquidcrystal molecules 190′ to an opposite direction in what is commonlyreferred to as a “disclination region” illustrated as region d1.Unfortunately, the transmission of light through the disclination regionis typically nonuniform and in a normally white display, light may beallowed to pass through the disclination region even when the pixelelectrodes 7 are biased to provide a black display image. When thisoccurs, the contrast ratio of the display is adversely affected.However, according to the present invention, the light blocking lines 9are designed to block light which otherwise would be pass through thetransparent substrate 100 (from a backlight) and into the disclinationregion. Here, the light blocking lines 9 are typically patterned to bewider than the disclination region d1. Moreover, because the width ofthe disclination region d1 typically increases with any increase in stepheight associated with the pixel electrodes 7, the light blocking lines9 are spaced laterally from the data lines 150 so there is no overlaptherebetween which might increase the step height of the pixelelectrodes 7 (and also increase the magnitude of any parasitic loadcapacitance between the data lines 150). Finally, because the lightblocking lines 9 are positioned along only one side of the pixelelectrode 7, the opening ratio of the display device may be increased.

[0039] Referring now specifically to FIG. 6, the width of thedisclination region (shown as d2) may be reduced even further byimproving the planar uniformity of the pixel electrodes 7. According toanother preferred aspect of the present invention, this reduction in thewidth of the disclination region can be achieved by forming an organicelectrically insulating/passivation layer 220 on the inorganicinsulating layer 160. The organic insulating layer 220 preferablycomprises a layer of polyimide or an acrylic resin having a smooth uppersurface and a thickness in a range between about 5,000 and 7,000 Å. Inparticular, the organic insulating layer 220 is made sufficiently thickto offset step-height variations in the inorganic insulating layer 160.The organic insulating layer 220 may also be planarized usingconventional techniques to define a planarized upper surface on whichthe pixel electrodes 7 can be formed.

[0040] Referring now specifically to FIG. 7, the above-described methodof forming a liquid crystal display device may be simplified by omittingthe step of forming an inorganic insulating layer 160 which typicallyinvolves a chemical vapor deposition step. However, to compensate forthe missing inorganic insulating layer 160, an organic insulating layer220 may be formed to have a thickness in a range between about 15,000and 35,000 Å, however, thicker insulating layer 220 may also be used.This organic insulating layer 220 may also be planarized so that thepixel electrodes 7 have reduced step height. As will be understood bythose skilled in the art, increasing the thickness of the organicinsulating layer 220 increases the vertical distance between the datalines 150 and the pixel electrodes 7 and thereby reduces the magnitudesof the stray electric fields adjacent the spaces between the pixelelectrodes 7. As described above, this reduction in field strength andstep height reduces the width of the disclination region so thatd3<d2<d1. Accordingly, the widths of the light blocking lines 9 may alsobe decreased as the vertical spacing between the data lines 150 andpixel electrodes 7 is increased. Thus, increased opening ratios may beachieved by increasing the thickness of the passivation layer(s)disposed between the data lines 150 and pixel electrodes 7.

[0041]FIGS. 8 and 9 also illustrated two examples for limiting lightleakage in the upper and lower sides of each pixel. The two figures arecross-sectional views of the device of FIG. 4, taken along the lineD-D′. The view of FIG. 8 corresponds to an etch back type amorphoussilicon LCD apparatus, and the view in FIG. 9 corresponds to an etchstopper type amorphous silicon LCD apparatus. As shown in FIG. 8, anorganic black matrix layer 300 is formed to cover the end portions ofthe gate lines 130 a and storage electrode lines 130 b. The organicblack matrix 300 may have a thickness of about 8,000 Å or more for ahigher luminous intensity. Even though the step of the black matrix 300may raise the orientation disorder of the liquid crystal molecules 190′due to its thickness, the gate lines 130 a and storage electrode lines130 b can effectively block the leakage of light which may be caused bystep height of the black matrix 300 layer.

[0042] Referring now to FIG. 9, a black matrix layer 230 containingchromium is formed on the counter substrate 200. In this embodiment, thelight rays reflected on the black matrix 230 may be transmitted to thechannel region 10 of the TFT in the active matrix substrate, and thuslight leakage can occur since the light rays produce an induced currentin the channel region. However, since the amorphous silicon film layer110 is formed very thin in the etch stopper type TFT, this light leakagecan be considerably reduced.

[0043] In the drawings and specification, there have been disclosedtypical preferred embodiments of the invention and, although specificterms are employed, they are used in a generic and descriptive senseonly and not for purposes of limitation, the scope of the inventionbeing set forth in the following claims.

That which is claimed is:
 1. A liquid crystal display device,comprising: a transparent substrate having a face thereon; a firstdisplay cell on said substrate, said first display cell containing afirst pixel electrode and a control input electrically coupled to afirst gate line; a first light blocking line on said substrate,electrically coupled to said first gate line; a second display cell onsaid substrate, said second display cell containing a second pixelelectrode which overlaps said first light blocking line, and a controlinput electrically coupled to a second gate line; and a first data lineon said substrate, said first data line overlapping said first andsecond pixel electrodes but not overlapping said first light blockingline.
 2. The display device of claim 1 , wherein said first lightblocking line extends parallel to said first data line.
 3. The displaydevice of claim 2 , wherein said first light blocking line extendsorthogonal to said first gate line.
 4. The display device of claim 3 ,further comprising a second data line electrically coupled to said firstand second display cells; and wherein said first light blocking line isspaced closer to said first data line than said second data line.
 5. Thedisplay device of claim 3 , wherein said first light blocking line andsaid first and second gate lines have beveled edges.
 6. The displaydevice of claim 5 , wherein said first light blocking line and saidfirst gate line are contiguous.
 7. The display device of claim 6 ,wherein said first light blocking line and said first gate line comprisea patterned conductive layer containing a metal selected from the groupconsisting of aluminum, titanium and tungsten.
 8. The display device ofclaim 3 , wherein said first light blocking line and said first gateline are contiguous.
 9. The display device of claim 8 , wherein saidfirst light blocking line and said first gate line comprise a patternedconductive layer containing a metal selected from the group consistingof aluminum, titanium and tungsten.
 10. The display device of claim 8 ,further comprising a first electrically insulating layer on said firstlight blocking line and said first gate line, opposite the face; and asecond electrically insulating layer disposed between said first dataline and said second pixel electrode.
 11. The display device of claim 10, wherein said first data line, said first light blocking line and saidfirst gate line each have thicknesses of less than about 2000 Å.
 12. Thedisplay device of claim 1 1, wherein said second electrically insulatinglayer comprises an inorganic passivation layer of silicon nitride havinga thickness less than about 4000 Å.
 13. The display device of claim 12 ,further comprising an organic passivation layer containing a materialselected from the group consisting of polyimide and acrylic resins,between said second electrically insulating layer and said second pixelelectrode.
 14. The display device of claim 13 , wherein said organicpassivation layer has a polished upper surface in contact with saidsecond pixel electrode.
 15. The display device of claim 14 , whereinsaid organic passivation layer has a thickness in a range between about5000 Å and 7000 Å.
 16. The display device of claim 8 , furthercomprising a first electrically insulating layer on said first lightblocking line and said first gate line, opposite the face; and anorganic passivation layer containing a material selected from the groupconsisting of polyimide and acrylic resins, disposed between said firstdata line and said second pixel electrode.
 17. The display device ofclaim 16 , wherein said organic passivation layer has a thicknessgreater than about 15000 Å.
 18. The display device of claim 17 , whereinsaid organic passivation layer has a polished upper surface in contactwith said second pixel electrode.
 19. The display device of claim 7 ,wherein said second display cell comprises a thin-film transistor havingan amorphous silicon active layer extending opposite said second gateline.
 20. The display device of claim 1 9, further comprising an organicblack matrix layer extending opposite the active layer of said thin-filmtransistor.
 21. The display device of claim 20 , wherein said organicblack matrix layer has a thickness greater than about 8000 Å.
 22. Aliquid crystal display device, comprising: a transparent substrate; anarray of liquid crystal display cells containing a plurality of rows andcolumns of liquid crystal display cells therein, on said transparentsubstrate; a plurality of data lines on said transparent substrate, eachof said data lines disposed between adjacent columns of display cells;and a plurality of ladder-shaped electrodes on said transparentsubstrate, each of said ladder-shaped electrodes disposed opposite aplurality of pixel electrodes in a respective row of display cells. 23.The display device of claim 22 , wherein each ladder-shaped electrodecomprises a plurality of spaced rungs which extend parallel to saidplurality of data lines.
 24. The display device of claim 23 , whereineach of the rungs of a ladder-shaped electrode comprises a lightblocking line which overlaps a respective pixel electrode in a row ofdisplay cells.
 25. The display device of claim 24 , wherein the datalines do not overlap the rungs of the ladder-shaped electrodes.
 26. Thedisplay device of claim 22 , wherein each ladder-shaped electrode iscomprised of a gate line along a first side thereof which iselectrically coupled to one row of display cells, a storage capacitorelectrode along a second side thereof which is electrically coupled topixel electrodes in another row of display cells and a plurality oflight blocking lines which electrically connect each gate line to arespective storage capacitor electrode.
 27. The display device of claim26 , wherein each ladder-shaped electrode has beveled edges.
 28. Thedisplay device of claim 26 , further comprising an organic passivationlayer containing a material selected from the group consisting ofpolyimide and acrylic resins, between said plurality of data lines andthe pixel electrodes in said array of liquid crystal display cells. 29.The display device of claim 28 , wherein the organic passivation layerhas a polished upper surface in contact with the pixel electrodes insaid array of liquid crystal display cells.
 30. A method of forming aliquid crystal display device, comprising the steps of: forming a firstconductive layer on a face of a transparent substrate; patterning thefirst conductive layer to define a ladder-shaped electrode having firstand second side electrodes and a plurality of rungs electricallyinterconnecting the first and second side electrodes; forming a firstelectrically insulating layer on the ladder-shaped electrode; forming alayer of amorphous silicon on the first electrically insulating layer;patterning the layer of amorphous silicon to define an amorphous siliconactive region extending opposite the first side electrode; forming asecond conductive layer on the first electrically insulating layer andamorphous silicon active region; patterning the second conductive into adata line and a drain electrode so that the data line and drainelectrode contact first and second portions of the amorphous siliconactive region, respectively; forming a second electrically insulatinglayer on the patterned second conductive layer; patterning the secondelectrically insulating layer to expose a portion of the drainelectrode; and forming an indium-tin-oxide pixel electrode electricallyconnected to the exposed portion of the drain electrode.
 31. The methodof claim 30 , wherein said step of patterning the second conductivelayer comprises patterning the second conductive layer into a pluralityof data lines which extend parallel to but do not overlap the pluralityof rungs of the ladder-shaped electrode.
 32. The method of claim 31 ,wherein said step of forming a pixel electrode comprises forming a pixelelectrode which overlaps a respective data line and a respective rung ofthe ladder-shaped electrode.
 33. The method of claim 32 , wherein saidstep of patterning the first conductive layer comprises patterning thefirst conductive layer to define a ladder-shaped electrode havingbeveled edges.
 34. The method of claim 32 , wherein said step of forminga pixel electrode comprises forming a pixel electrode which overlaps thefirst and second side electrodes.
 35. The method of claim 33 , whereinsaid step of patterning the second electrically insulating layer ispreceded by the steps of forming an organic passivation layer on thesecond electrically insulating layer and then planarizing the organicpassivation layer; and wherein said step of forming an indium-tin-oxidepixel electrode comprises patterning a layer of indium-tin-oxide on theplanarized organic passivation layer.
 36. The method of claim 33 ,wherein said step of forming a second electrically insulating layercomprises forming an organic passivation layer containing a materialselected from the group consisting of polyimide and acrylic resins, onthe patterned second conductive layer.